I learned quite a bit about Shimano Di2 when I installed one of the first available Time Trial/Triathlon groupsets on my Cervelo P2. I’ve subsequently answered a lot of questions on forums and article comments, and elsewhere. In doing so, I realized that people have a lot of questions about Di2 and the answers are difficult to find. This lead me to create this article, to consolidate everything I know and have been asked into one location so people can find answers. If you can’t find what you’re looking for below, please leave a comment and I’ll do my best to help.

Index: There’s lots of info in this post, so here’s an Index to help you find specific sections:

System Overview: Shimano Di2 Dura-Ace 9150 and 9070 and Ultegra 6770 and 6870

The second generation Shimano Ultegra 6770/6870 and Dura-Ace 9070 “E-Tube” electronic bicycle shifting systems consist of battery-powered electric derailleurs activated by handlebar mounted push buttons. Power and shift commands are sent via a 2-wire CAN (Controller Area Network) datalink contained within a single cable housing. This design has several advantages over conventional mechanical shifting systems, the most notable of which are:

Greatly improved shift quality, especially for the front derailleur chainrings, allowing shifting under full power with almost no chance of a dropped chain.

Shifting is available at multiple positions on the handlebars, for example, at the end of the time trial aero bars, on the brake levers, up to in climbing position, and down low the sprint position.

Automatic trimming of the front derailleur position as the rear derailleur moves back and forth between the smaller and bigger gears. This eliminates unintended contact (and noise) between the front derailleur and the chain.

Multi-Shift: Pressing and holding a rear derailleur shift button results in shifts through multiple gears. The rate of shifts can be configured using the PC computer interface cable and the free Shimano E-tube Project software.

Synchronized Shifting: Starting with Dura-Ace 9150, automated Synchronized Sifting of the front derailleur is an option. Two SHIMANO Synchronized Shift modes will be available:

Full SHIMANO Synchronized Shift: the front derailleur reacts based on the rear derailleur’s shift action. This essentially means that, when activated, there is no need for two separate shifters to control front and rear derailleurs, the two buttons on one shifter will control both derailleurs.

Semi SHIMANO Synchronized Shift mode: the rear derailleur reacts based on the front derailleur’s shift action, shifting to the next most appropriate rear gear when the rider makes a front shift.

R9120, R9170 – syncroshift enabled with firmware 3.2.0 or newer

6870, 9070 – syncroshift enabled with firmware 3.2.1 or newer

6770 – no syncroshift firmware update will be offered

Historic Info on the older first generation 5-wire Shimano Dura-Ace Di2 DA-7970 system and how it compares to the new E-tube 2-wire system:

Released in 2009, the 7970 operated using a very basic 5-wire electronic system. Each shift button was connected to a different wire; shorting the specific wires together controlled the derailleur upshifts and downshifts. Because the first generation 7970 used completely different technologies than the newer 2-wire systems, none of the components are cross-compatible. At this point, Shimano is not expected to offer any updates or new components using the first generation 7970 architecture; everything from now on will be based on the newer 2-wire E-tube design. The second generation design offers several advantages, which include: 1) smaller wire size, smaller connector size, waterproof connectors; 2) all switches can be reconfigured in software to send upshift or downshift commands to either the front or rear derailleur; 3) firmware updates can add new features (such as multi-shift) and compatibility with new components.

The confusing naming system used by Shimano makes it difficult to figure out what each component is, much less what is compatible between systems. Here are some compatibility guidelines:

Nothing from the first generation (4-conductor / 5-conductor) Dura-Ace Di2 7970 system is compatible with any other newer system. It was replaced by the (2-conductor) E-tube systems. No parts are inter-operable between 7970 and any other Di2 System.

In general, every electronic Di2 component is compatible between the Ultegra 6770, 6870, and Dura-Ace 9070 systems (see exceptions below.) This means that all of the road bike Ultegra/Dura-Ace dual control brake levers/shifts, time trial shifters, and climbing shifters can be used with either Ultegra 6770/6870 or Dura-Ace 9070 front and rear derailleurs. Any of the Ultegra/Dura-Ace controllers (A Junctions) can be used with either system. All components use the same cables and connectors.

Synchronized Shifting and Bluetooth Wireless Units can be added to all E-tube Ultegra and Dura-Ace systems but the battery has to be upgraded to the BT-DN110 Internal Battery or BM-DN100 External Battery Mount. To add Bluetooth capability, a EW-WU101 or EW-WU111 inline transmitter must be added to road bikes and for mountain bikes, the SC-MT800 or SC-M9051 display/transmitter unit must be added.

Compatibility Exceptions:

Note 1 – Sprint Shifter Exception: The Sprint Shifter is the only exception for shifter incompatibility. It has a different wiring connector (and internal components) that can only plug into a unique/dedicated third port on the Dura-Ace ST-9070 Dual Control Brake Levers/Shifters and also the ST-6870 Levers. There is no sprint shifter port on the ST-R785 Hydraulic Levers.

Note 2 – Can’t mix 10-speed/11-speed front/rear Derailleurs: It is no longer possible to use a 10-speed front derailleur with an 11-speed rear derailleur (and 11-speed front with 10-speed rear.) See note farther below to read the history on this if you want all the messy details.

Note 3 – Front A junction and Internal Battery: Since the February 2015 firmware update, the older SM-EW67-A-E Front Junction A is no longer compatible with the BTR2 Internal Battery. The SM-EW90 Front Junction (with integrated charging port) should be used instead. The SM-EW67 still works with the external battery.

Note 4 – Update the Firmware to make components compatible: If the firmware on all components is not updated to the latest version, some components may be not operate correctly with one another. So download the latest E-tube software and update everything and it should work.

Note 5 – All Shifters work with all 10-speed and/or 11-speed Rear Derailleurs: All of the shifters are compatible with either the 10-speed Ultegra 6770 or 11-speed Ultegra 6870/Dura-Ace 9070 systems as long as they all have the latest firmware. The rear derailleur is the only component that “knows” or “cares” how many rear gears are available. The shifters only send upshift/downshift commands and do not “know” or “care” which gear is currently selected and how many total gears there are.

Note 6 – SM-BTR1 External Battery and SM-BMR1 Mount firmware updates: The more expensive dedicate service tool (SM-PCE1 PC Interface) must be used to upgrade the firmware on the external battery/mount.The external battery and battery mount can not receive firmware upgrades via the SM-EW90 Front Junction A and the SM-BCR2 PC Interface/Battery Charger. (The SM-EW90 will work in a system with an external battery, but a firmware update can cause them to become incompatible until both are updated independently using the appropriate PC Interface and the Shimano E-Tube Project software.)

Compatibility: 11-Speed Rear Derailleur and 10-speed sprockets/wheels

The 11-speed Dura-Ace 9070 and Ultegra 6870 rear derailleurs are designed exclusively for 11-speed rear sprockets and 11-speed Front Derailleurs. Shimano does not provide a way to recalibrate/reprogram them for a 10-speed setup. The sprocket spacing is slightly smaller and the overall range of travel slightly longer on 11-speed systems. If you have 10-speed wheels and 10-speed sprockets, you should use the 10-speed RD-6770 rear derailleur and a 10-speed FD-6770 front derailleur.

Similarly, a 10-speed RD-6770 rear derailleur should not be used with 11-speed sprockets. There will be chatter in some gears, and there might be slow-shifts or self-shifts.

It doesn’t matter which shifters are used; the shifters send upshift/downshift commands regardless of which derailleur config is being used. Shifters do not “know” or “care” which gear is currently selected and how many total gears there are.

Front Chain Rings: In general, most any front chain rings will work, rigid forged rings work best with Di2 due to high front derailleur shift forces. Shimano chain rings tend to be the best, but most others work as well. A 10-speed specific or 11-speed specific chain should be used, but the differences between them are minimal and can generally be mixed/matched without issue.

How to convert “non-upgradeable 10-speed only” wheels such as Zipp 900/Sub9 Disc Wheels to 11-speed: “the spacing between a Campy 11 and Shimano 11 is close enough that you can use the cassettes interchangeably. If you get a Campy free hub body, the 2 shims (part# is on the Zipp website, just search for Campagnolo 11) and a Campy cassette and you’re ready to ride with all 11 cogs available to use.” via slowtwitch.com

But it’s an emergency and I need to use a 10-speed wheel. . . In emergency situations, 11-speed rear derailleurs can be used with 10-speed sprockets. There will probably be chatter in some gears, and there might be slow-shifts or self-shifts. To setup an 11-speed rear derailleur for a 10-speed sprocket setup, adjust the mechanical limit screw so that it can’t shift into the missing 11th sprocket position, then follow the rear derailleur adjustment procedures listed below.

Included for very motivated individuals only: 10-speed front derailleurs can be used with 11-speed rear derailleurs if the shifters and battery have firmware installed from E-tube software version 2.5.2 or earlier. Shimano disabled support for this 11-speed and 10-speed cross-matching with later firmware updates. For informational purposes only, the details of how to regain compatibility are detailed below.

Important Notice 2014-07-14: There is a compatibility issue with Shimano e-Tube software/firmware versions v2.6.0 and later that prevents 10-speed front derailleurs (FD-6770) from working with 11-speed rear derailleurs (RD-6870) and 11-speed front derailleurs (FD-6870) from working with 10-speed rear derailleurs (RD-6770). DO NOT UPDATE FIRMWARE using Shimano e-Tube software v2.6.0 or later if you are mixing an FD-6770 front derailleur and a RD-6870 11-speed rear derailleur, or a FD-6870 with a RD-6770.

The problem component is the battery (external battery mounts SM-BMR1 and SM-BMR2, internal seat post battery SM-BTR2.) If you keep battery firmware at v2.0.6 or earlier, the system will continue function properly. Shimano e-Tube Software v2.6.0 will update battery firmware to v3.0.5, and will not allow the RD-6870 to work with a FD-6770 setup.

If the battery firmware is updated to 3.0.5, it CAN NOT be rewritten back to the older version. You will need to need to replace a derailleur so that both are 6770 10-speed or so that that both are 6870 11-speed. (The other option is to get get a battery with the older firmware and never update it.)

Here’s a link to the “last known good version” of the Shimano e-Tube software to work with a mixed 10-speed/11-speed system: E-tube_Proj_V_2_5_2.zip Use this version and do not connect to the internet when using it so that E-tube can’t check for updates when open.

To roll-back newer versions of battery and shifter firmware, install E-tube version 2.5.2 and made a copy of “C:\ProgramData\E-tube Project\FW” which has all the firmwares packaged in that version of E-tube. Next, install the latest version of E-tube. Then copy all the firmwares from the the 2.2.3 version back to the same location “C:\ProgramData\E-tube Project\FW” for the latest version. Next, the trick is to find the firmware you want to downgrade (pretty easy from the name and version in the file name), and then rename it to the same name as the latest version, but increment the last version digit by one. Then connect to the bike with E-tube (without an internet connection) and it will identify that a firmware upgrade is available for that component and allow you to do the firmware “upgrade” to the older version of firmware. Now exit E-tube and then rename the firmware file back to original to prevent issue in future. E-tube will then try to upgrade again but just don’t let it do that. This should get a bike that did nothing (not even enter adjustment mode) to a fully working state by reverting the battery and shifters. Running latest firmware in derailleurs seems to be fine. (thanks to commenter vosadrain)

It will not be possible to charge the BTR2 internal battery using the BCR2 USB charger unless you also downgrade the firmware of the BCR2 USB charger as well.

Note however that latest E-tube software will say the setup is unsupported and will not allow programming. To do programming, disconnect the internal battery and connect a spare external battery. This allows making settings changes. To program the BTR2 itself, I just connect to the BTR2 by itself (no other components) and the E-tube software will allow firmware changes to it. Or try using the 2.5.2 version of E-tube.

Alternatively, buy a Di2DIY internal seat post battery kit and you will not have to go through the firmware downgrading. The kit makes it possible to run all components with the latest E-tube firmware. Also worth noting some firmware updates were done to fix power distribution errors in the FPGA’s that would allow the batteries to drain down when the bike was just sitting.

Checking Battery Charge Level:

A single battery charge should give at least 1500 miles of riding. Most riders will not need to charge the battery more than twice a year.

To check the battery charge remaining, press and hold any shifting switch for 0.5 seconds or more. The amount of battery charge remaining will be indicated by the light on Front Controller A Junction.

100% remaining: Illuminates green (for 2 seconds)

50% remaining: Flashes green (5 times)

25% remaining: Illuminates red (for 2 seconds)

0% remaining: Flashes red (5 times)

When the battery charge is low, first the front derailleur will stop operating, and then the rear derailleur will stop operating. When the battery charge has been fully spent, the derailleurs will be fixed at the last gear shifting position. If the battery indicator is illuminated red, it is recommended that you recharge the battery as soon as possible.

Adjusting the Rear Derailleur Trim:

If you switch between multiple rear wheels, it’s very likely that the sprockets on different wheels won’t be in exactly the same relative position to the rear derailleur, resulting in that annoying clicking sound as the chain makes contact with an adjacent sprocket. Follow the steps below to properly align the rear derailleur with the rear sprockets.

Shift the rear derailleur to the 5th sprocket position. Press the button at the junction (A) of the SM-EW67-A-E until the red LED illuminates in order to switch to rear derailleur adjustment mode. Note that if you keep pressing the button after the red LED has illuminated, protection recovery operation will begin.

If shifting switch is pressed once while the initial setting condition is active, the guide pulley will move one step toward the inside. If shifting switch (Y) is pressed once, the guide pulley will move one step toward the outside.

Note: The guide pulley can move 15 steps inward and 15 steps outward from the initial position, for a total of 31 positions.

Note: When adjusting, the guide pulley will overrun slightly and then move back in an exaggerated movement so that you can check the adjustment direction. When checking the positions of the guide pulley and the sprocket, check at the position where the guide pulley finally stops.

While turning the front chainwheel, operate shifting switch to move the guide pulley toward the inside until the chain touches the 4th sprocket and makes a slight noise.

Next, operate shifting switch 4 times to move the guide pulley toward the outside by 4 steps to the target position.

Press the button at junction (A) until the red LED turns off in order to switch from rear derailleur adjustment mode to gear shifting mode. Shift to each gear and check that no noise is generated at any gear position. If fine adjustment is needed, switch back to adjustment mode and readjust the rear derailleur.

Note: if you have customized your shifters and swapped buttons, this will change which shifter and buttons control the micro-adjustments. Also, if you hit the wrong buttons while trying to set the FD trim, you can actually alter the setup of your RD. Be certain that you’re hitting the correct adjustment buttons.

If you have a Garmin or similar head unit and a SM-EWW01 ANT module, the display will automatically switch into derailleur trim display when you activate that mode (i.e. by pressing the button at the junction (A) of the SM-EW67-A-E.) It will give you the trim position in either + or – 12 positions. When switching wheels, simply take note which position suits which wheel/sprocket/trainer, and trim to that level each time you change. This removes the guesswork and makes changing from wheel to trainer simple.

Note on FD-6870 Front Derailleur Trim:

The FD-6870 trim adjustment effects the auto-trim positions. The adjustment feature is accessible via either the A-Junction box, or the “Front derailleur adjustment setting” in the e-tube software, and should be used only after you have already set the physical inner/outer limit screws. So for example, if the FD outer plate rubs the chain when using the 6th largest cog, you would want to adjust the FD trim outward a couple ticks. However, you can only perform this adjustment while in the big-ring/big-cog combination. Etube forces the derailleurs into this maximum cross-chained position, whereas during the manual method you must shift to these positions yourself. (Thanks to commenter Bryan B for the info.)

Dealer Manuals:

The dealers manuals contain the most detailed information available from Shimano. If you’re looking for detailed installation instructions, check here:

Shimano E-tube Project Wireless for iOS and Android: Announced on April 15, 2016 but as of yet unreleased, these apps will allow configuration of shift profiles (multi-shift on/off, multi-shift delay between shifts, shifter button assignments) and firmware updates over Bluetooth. To function, a Shimano Di2 Bluetooth Adapter, such as the MT800 digital display, is required.

Shimano E-tube Project Windows PC Software: This free software is used to update the firmware of all components. It works with the SM-BCR2 Charger + USB Adapter and the SM-PCE1 Diagnostic Adapter. The software is used to change the configuration of each shift button / lever (any can be programmed to upshift or downshift either the front or the rear derailleur.) It can also be used to enable multi-shift (multi-shift is where the shifter is held and the rear derailleur shifts through multiple gears until the shifter is released.) The delay between of the gear changes during multi-shifting can also be adjusted. The software is available from http://e-tubeproject.shimano.com/
Older versions of the e-tube software are available from these links: 2.5.2

PC & Mobile Interfaces, Chargers, and Software:

SM-BCR1 Battery Charger: This is used to charge the external battery. The part number for the battery charger wall cord is SM-BCC1.

SM-BCR2 Charging and PC Connection: for SM-EW90-A 3-port and SM-EW90-B 5-port A Junctions. This plugs into a special port on the side of the A junctions (which is covered by a rubber flap.) This adapter charges the internal battery when first plugged into the A junction; it must be powered by a standard USB Wall charger (such as that used for an Apple iPhone) or a PC that is powered-on. If the Shimano E-Tube Project Software is launched on the Windows PC with the SM-BCR2 attached, the SM-BCR2 will switch from charging mode to configuration mode. It must be detached from the computer and reattached to switch back to charging mode.

It takes about 2 hours to charge the internal battery.

Amber light=charging.

Light turns off when done.

If the Amber light does not come on when plugged in, this indicates battery is not discharged enough to charge.

Light flashing indicates something is wrong, like trying to charge a external battery through a BMR.

Junction A Charger Port and Charger/PC Diagnostic Cable

Hacking the SM-BCR2 to have a standard Di2 cable connector: If your 3-port or 5-port junction is inaccessible for charging, there is an alternative hack method to connect it to the system through a standard Di2 port. With basic soldering skills you can hack the BCR2 to be used with any setup. Buy any length EW-SD50 wire, cut off one end. Cut the wire on the output side of the BCR2. Splice the two wires together, so that the output wire of the BCR2 is now a standard Di2 connector. The charger has an inner (white) and outer (shield) wire; connect the inner white wire to the SD50 red wire; connect the charger outer shield wire to the SD50 black wire. You will then be able to plug the BCR2 into any Di2 port . Or use a SM-JC40 junction B and another length of EW-SD50 wire and go through the RD (by using the SM-JC40 to connect the rear derailleur, new output wire of the EW-SD50 , and the wire that ordinarily connect the rest of the system to the rear derailleur.)Thanks to @Di2diy for the info.

SM-PCE1: This PC Configuration and Diagnostics adapter will not charge the internal battery. It offers the same configuration options as the SM-BCR2, but also add some advanced diagnostic and troubleshooting features that the SM-BCR2 does not have. It attaches to via the standard E-tube wire (just like the EW-SD50 cables) rather than to a dedicated port on the side of the front A junction.

Bluetooth and E-tube Apps for Apple iOS and Android: Bluetooth wireless modules are available to allow system settings to be adjusted via the mobile applications that connect via Bluetooth Adapters.

Component Overview:

The confusing naming system used by Shimano makes it difficult to figure out what each component is, much less what it does and how it fits into an a complete Di2 system. Here’s an overview of all the major Ultegra and Dura-Ace Di2 components.

Dual Control Brake Levers/Shifters (a.k.a. Brifters):

ST-6770 Ultegra Road Dual Control Brake Levers/Shifters: The Ultegra version can be used with the climbing shifters. They are sold in in left/right pairs and are also available separately.

ST-9070 Dura-Ace Road Dual Control Brake Levers/Shifters: The main advantages these have over the ST-6770 version is slightly lighter weight and compatibility with the low-mount sprint shifters. As like the Ultegra version, they are compatible with the climbing shifters. They also have hidden button under the rubber hoods that can activate screen changes on cycling computers from Garmin, Magellan, Pioneer, and Shimano (Shimano SM-EWW01 ANT Wireless Broadcast Module required.)

ST-9071 Dura-Ace Time Trial/Triathlon Dual Control Brake Levers/Shifters: These levers provide shifting from the pursuit bar position on time trial bikes. There is no Ultegra option offered at this time. These are available as left/right pairs, or can be ordered separately. These do have a permanently attached wire with a male end for connection the the SM-EW90 front “A” junction. Combined weight both levers: 117 grams.

ST-R9160 (standard cable brakes) and ST-R9180 (hydraulic brakes) Time Trial Dual Control Brake Levels/Shifters: These are the lower-profile shifters offered with the newer Dura-Ace R9150 groupset.

ST-6871 Ultegra Time Trial/Triathlon Dual Control Brake Levers/Shifters: Ultegra version of the ST-9071 Dura-Ace shifters. Slightly heavier and much less expensive than the Dura-Ace version. Combined weight both levers: 142 grams.

ST-R785 Hydraulic Road Dual Control Brake Levers/Shifters: These hydraulic road shifters are compatible with both the climbing and sprint shifters. These are compatible with the SM-RT99 centerlock 140mm and 160mm rotors and WH-RX31 wheelset (which as no standard rim brake track.) These require the BR-785 dual piston hydraulic disc calipers. They do not have the special wiring port required for the SW-R610 Sprint Shifters and a SM-EW90-B 5-port junction A is required to use the SW-R600 climbing shifter.

ST-6870 Ultegra Road Dual Control Brake Levers/Shifters: These road shifters are compatible with both the climbing and sprint shifters.

Dedicated Shifters:

SW-R671 Dura-Ace 2-Button Time Trial/Triathlon Bar End Shifters: These shifters are installed on the end of time trial aero bars. By default, the left shifter upshifts/downshifts the front derailleur; the right controls the rear derailleur. For both, the lower button upshifts into a harder gear and the upper button downshifts to an easier gear. This can be changed using the Shimano E-tube Project software; the functions of the left and right sifters can be switched with one another as well. These are available in pairs or separately.

SW-9071 Dura-Ace 1-Button Time Trial/Triathlon Bar End Shifters: These shifters have only one button each and are intended to control only the rear derailleur, with one sending the upshift command and the other the downshift command. (I personally think this version is absolutely worthless. Why have 2 SW-9071 shifters at twice the price and twice the weight, when you can just buy a single SW-R671 Right shifter instead.)

SW-R600 Climbing/PAVE Shifter: This shifter is for road bikes and is mounted on the upper horizontal portion of the handlebar, or any other location comfortable for the rider. They can be used in addition to the Dual Control Brake Lever/Shifter, or can be used on their own by plugging directly into a SM-EW90-A 3-Port Junction or SM-EW90-B Dura-Ace 5-Port Junction.

SW-R610 Dura-Ace Sprint Shifter: This is the only component using a unique wiring connector; it is only compatible with the ST-9070 Dura-Ace and Ultegra ST-6870 Road Dual Control Brake Levers/Shifters. Unlike all of the other shifters, the sprint shifters do not contain a circuit board; they do not show up as components on the CAN bus network. Instead, the sprint shifters are simple momentary switches that activate the circuit board on the host Dual Control Brake Lever/Shifter. The host dual control lever is what sends the shift command. (Note: Any momentary switch can be attached to the sprint shifter port on the Dual Control Levers by splicing into a standard EW-SD50 wire to act as remote shifters.)

Alfine SW-S705 Right Flat-Bar Shifter: Reported to work with other non-Alfine setups.

SW-R9160 Time Trial bar-end shifters (pair): These are-end shifters directly control the rear derailleur, with one for the upshfit and one for the downshift. The front derailleur is controlled automatically via automatic Synchronized Shifting. These shifters require the BT-DN110 Internal Battery for synchronized shifting.

SW-R9150 Climbing shifters (pair): These tiny climbing shifters are about as small as the sprint shifters, but can be directly connected to a junction box and do not have to be connected as slave buttons to a brake/shift lever special port. They come with plastic mounts to make it easier to attach to bars beneath bar tape. They are ideal for synchronized shifting, with one controlling the upshifts and the other downshifts. These shifters require the BT-DN110 Internal Battery for synchronized shifting.

Rear Derailleurs:

RD-9070: Dura-Ace 11-Speed Rear Derailleur, lighter weight version on which the RD-6870 is based.

RD-R9150: Dura-Ace 11-Speed Rear Derailleur with 30-tooth sprocket compatibility and modified “Shadow RD” geometry to keep the mechanism close to the rear wheel to help avoid damage in the event of an accident.

Alfine SG-S505 and SG-S705: The Shimano series targets comfort and urban bikes. It uses an 8-speed (505) or 11-speed (705) internal epicyclic rear hub. It is believed to be compatible with other Di2 ETube components but this has not been verified.

Display / Wireless Communication:

SM-EWW01 ANT Wireless Broadcast Module: This module wirelessly broadcasts Di2 data (front and rear gear selection details, gear ratio, battery life) to a cycling computer using the ANT protocol. It is compatible with Dura-Ace 9070, Ultegra 6870 Di2 and Ultegra 6770 E-tube road shifting systems. SM-EWW01 plugs into the E-tube wiring system between existing components. It has an 2 wiring ports, so it can be connected between a front shifter and the Front Junction A, or at the rear derailleur (between rear derailleur and Etube wire.) It transmits through a proprietary private ANT wireless protocol, which may eventually become a standard public ANT+ protocol. It is powered by the same Di2 system battery. It is currently compatible with the Garmin Edge 1000, Mio 505, and the PRO SCIO cycling computers (with more to come.) The hidden buttons under the hoods of the 9070 shifter levers will switch screens on the cycling computer when paired with this module. It does not currently allow for shifting control from a cycling computer/device and it is not clear that this functionality will ever be offered. The SM-EWW01 is 38mm long, 25mm wide, 12.5mm high, and weighs less than 5 grams. It does not come with any wires; 1 wire would have to be added if adding this module to an existing Di2 system.

EW-WU101 and EW-WU111 ANT and Bluetooth Wireless Broadcast Modules: These modules are similar to the SM-WEE01 but also include Bluetooth capabilities in addition to ANT capabilities. They require the BT-DN110 battery or the BM-DN100 Battery Mount and can not be used with the SM-EW67 Front A Junction.

SC705 Alfine Display Unit: This unit displays the battery level and the rear derailleur gear selection. It is powered by the system battery and has a port for the SM-BCR2 internal battery charger / USB diagnostic tool. It is primarily designed for Alfine systems (both 8 505-series and 11 speed 705-series). It is compatible with Ultegra and Dura-Ace Di2.

MT800 Digital Display with Bluetooth: Primarily aimed at XT mountain bike applications, this display allows toggling between the 3 synchronized shift modes (where both both derailleurs are intelligently coordinated in unison by one pair of buttons, so no need for discrete shifting of the front derailleur.) It also shows battery level, gear position, shift mode and FOX iRD suspension position. The Digital Display required the new BT-DN110 battery. Existing Di2 XT systems are upgradable to be compatible with the new digital display after battery upgrade and firmware upgrade. This display has 3-port Di2 Cable junction and charging port integrated into the back and serves as a Front A Junction.

Batteries and Battery Mounts:

The batteries contain the main controllers for the system. It is therefor required to upgrade the battery to get features released in new versions of Di2 (such as Synchronized Shifting that automatically controls the front derailleur based on rear derailleur shifting.)

SM-BTR1 External Battery: This external battery must be used with the SM-BMR1 battery mount. It is removed from the mount and charged using a dedicated charger.

SM-BMR1 and SM-BMR2 External Battery Mount: This mount attached to bottle cage mount points or other dedicated frame mounts. It is available in 3 different mount lengths: -I (intermediate length), -S (short length), -L (long length). The SM-BMR2 is an updated version of the SM-BMR1.

SM-BTR2 Internal Battery: This battery is typically mounted in the seat post or seat tube of the frame. It is charged by plugging the SM-BCR2 Charging Cable/PC Adapter into the SM-EW90-A or SM-EW90-B Front A junctions.

Front A Junctions:

SM-EW67-A-E Ultegra 3-Cable Junction: This is the original front junction with 2 integrated cables to connect to the dual control brake lever/shifters. The male cable ends on this Front A Junction will not mate directly to the male cable ends on any of the Time Trial/Triathlon dual control brake shift levers or shifters; SM-JC41 Rear B Junctions can be used to connect this front A junction to TT/Triathlon shifters. This Junction works only with External Batteries, not Internal Batteries.

SM-EW90-A Dura-Ace 3-Port Junction: This front “A” junction is most commonly used in road bike setups. 2 ports connect to the dual control brake / shift levers; the third port is for the cable that leads to the bottom bracket junction.

SM-EW90-B Dura-Ace 5-Port Junction: This front “A” junction is primarily used in the Time Trial / Triathlon setups. 2 of the port are for the brake/shifter dual control levers, 2 of the ports are for the aer0 bar bar-end shifters, and the 5th port is for the cable that runs to the bottom bracket (where the B junction joins the wires from the front A junction, front derailleur, rear derailleur, and battery.)

EW-RS910 Internal Bar-end Junction: This junction is installed into the end of a bar or in a dedicated frame port. It facilitates internal cable routing.

B Junctions:

SM-JC41 Internal Junction: This version has the exact functionality as the SM-JC40 external version, but doesn’t have the mounting tab for being bolted to the bottom bracket or wrapping the extra cable lengths. It has 2 ports on one end and 2 on the other, making it more compact. In addition to being located at the bottom bracket to connect the A junction, battery, front derailleur, and rear derailleur, it can be used at the handle bars to join multiple shifters prior to being connected to the A Junction.

SM-JC40 External Junction: This version is intended to be attached to the frame using the bolt that is commonly located underneath the bottom bracket housing. This junction contains no electronics; it’s sole purpose is to join 4 connectors together, which are usually the wire from the front A junction, the battery, the front derailleur, and the rear derailleur. There are wire holders above the housing to capture the extra wire length by wrapping it back-and-forth.

Cables, Grommets, and Cable Remove/Install Tool:

EW-SD50 Cables: These cables connect the front A junction, the battery, the front derailleur, and the rear derailleur to the rear B junction, which is typically located near the bottom bracket (near the cranks.) These are available in lengths of 300mm, 350mm, 400mm, 500mm, 550mm, 600mm, 700mm, 750mm, 950mm, 1000mm, 1200mm, 1400mm.

SM-GM01 Grommet: These round grommets are used when drilling round holes for internal cable routing, or with existing round holes. The required hole diameter is 6mm (6mm = .236 inches. Use a 7/32-inch drill bit and then “wallow-out” the hole to make it a little bigger; a 1/4-inch drill bit will work but is just slightly larger than necessary.)

Shimano TL-EW02 Ultegra DI2 E-Tube Tool: This tool is used to connect and disconnect the Etube wires. They are extremely difficult to connect/disconnect by hand, and pliers or other tools can damage the wires. Don’t get this confused with the TL-EW01 tool, which is for the older 5-wire 7970 cables. (My Dura-Ace TT Dual Control Levers came with one of these tools, but no other components did.)

Common Questions (via Shimano):

Note: it is not necessary to replace the FD from upgrading from 10-speed to 11-speed.

What Components do I need to put together my own Di2 system?

Because of the huge number and variety of components, it’s very difficult to figure out what is actually necessary and what is optional. So here is a list, for the setup I recommend: Ultegra 6870. It starts from the handlebars and works backwards. (This assumes both front and rear derailleurs, but you actually don’t have to have both; you can pick one or the other and only the corresponding front shifter to go along with it.)

Any Type of Shifters / Shift Buttons. The Dual Control Brake Levers/Shifters are not required. You can get the just the climbing shifters or Triathlon/TT bar-end shifters, and then potentially add the Dual Control Levers/Shifters at a later point. (The only exception is the Sprint shifters, which require specific Dual Control Levers/Shifters with special ports as noted elsewhere in this article.) Amazon.com link

EW-SD50 Wires 1 and 2 between the front shifters and the Front Junction A (0nly for some shifters). This is a bit confusing, because some of the front shifters come with wiring attached to them and some of them require purchasing separate wires. In general, most of the stand-alone shifters come with wiring, as do the TT/Triathlon dual control shifters/levers, but the road dual control levers do not. Amazon.com link

Front Junction A. I recommend the SM-EW90-B 5-port front junction A as it provides the most upgrade flexibility; get the 3-port option only if you’re positive you’re never going to add more shifting components. The older SM-EW67-A-E has 2 wires built-in to connect with each of the dual control shift/brake levers; it doesn’t offer much flexibility or compatibility with a TT/Triathlon setup or adding additional shifters. Amazon.com link

Rear Junction B: This is where the wire from the front of the bike is connected to 3 output wires leading to the front derailleur, rear derailleur, and battery. SM-JC40 is for external wiring, SM-JC41 is for internal. Amazon.com link

Grommets for any place where the wire goes into the frame through a drilled hole. Amazon.com link

Front Derailleur. I recommend the Ultegra FD-6870 for 11-speed builds or the FD-6770 for 10-speed builds. The Dura-Ace FD-9070 is pretty much identical, just slightly (41g) lighter and 11-speed only. (I do not recommend the Ultegra FD-6770 unless you have a 10-speed setup, because of firmware compatibility issues with 11-speed rear derailleurs. Also, it is an older design than the FD-6870, so it is larger and offers slightly less shifting force.) Amazon.com link

Battery and Charger. Internal or external, depending on the build. If you have to skill/time/money-to-pay-someone to get everything internal, I highly recommend that option. The SM-BTR2 internal battery has more advanced integrated electronics and is better for firmware upgrades with the SM-BCR2 internal battery charger/PC tool. If you go with the SM-BTR1 external battery, you will need the SM-BMR1 external battery mount and SM-BCR1 external battery charger. Amazon.com link

Rear Derailleur. I recommend the Ultegra RD-6870 for a new build if you have 11-speed compatible wheels with 11-speed sprockets, or the Ultegra RD-6770 if you have 10-speed wheels/sprockets. The system must be match front and rear derailleurs (both 6870 11-speed or both 6770 10-speed.) Amazon.com link

TL-EW02 Etube Wire Remove/Install Tool: It takes quite a bit of force to snap the wires in/out. You may think you can get it seated properly with just your fingers, only to then have the wire come loose because it wasn’t fully seated. It’s a good idea to keep one in your saddle bag. Amazon.com link

What wire lengths do I need? This question is impossible to answer correctly, as it’s highly dependent on the frame size and configuration. What I recommend is running string between the component mounting locations to measure the lengths. Be sure to add some extra length, as I find that wires seem to come up short pretty frequently, even when “adding a little extra” to start with. Nothing is more frustrating that having a wire that is 25mm too short. I recommend ordering a few extra wires of multiple lengths and then returning the unneeded/unused wires. As noted above, the standard wire lengths are 300mm, 350mm, 400mm, 500mm, 550mm, 600mm, 700mm, 750mm, 950mm, 1000mm, 1200mm, 1400mm. Do not cut/splice these wires; the connectors on the end of the wires are very small in diameter to start with and you’ll end up with a splice that is larger and less waterproof than you started with.

Acknowledgements: Special thanks to Di2diy for his continued help in the comments. Check out his Ebay store for custom Di2 batteries, harnesses, and components.

Technical Details of the Di2 CANBUS protocol and signaling

Thanks to commenter Ghislain for the details: “I reversed engineered the signal going to the RD. Since I did not have a special tap connector, I could only look at the actual signals in open loop (RD wire disconnected) on the wire going to the RD using an oscilloscope. First, I found that shift up and down are multiplexed on the same wire. A shift down would generate a positive 100 msec clean 8 volt pulse (varies between 50 msec to 500 msec depending on how long you hold the shifter). On the same wire, a shift up would generate a series of 2 msec pulses that would last the same time of a shift down pulse. Therefore, the RD has enough intelligence to discriminate between the 2 types of pulses. When you hold the button on junction A, a 140 msec pulse is generated. But since my RD wire was disconnected, the RD would not go in adjust mode.”

2,002 Comments

I have Shimano Di2 Systems on two road bikes. dura ace 9070RD/FD Levers R785-r-l battery BTDN110 and controller SM-E90-A and the other Ultegra 6870 RD/FD levers 6770R-L Battery BT DN110 and controller SM EW90-A. I have the latest e-Tube software. I setup autoshift using e-Tube on a PC and semi auto as well but I can not figure out how to activate autoshifting or whether I am still missing something? I press the SM-E90A twice to activate? but that doesn’t seem to work. I have the latest firmware on both systems — can you let me know what I am doing wrong? 52/36 chain ring, standard setup for the shift pattern loaded in the software.

Great site! I have a Cervelo S5 with standard Horn bars, 6780 shifter, aero bars and bar end shifters. I am using a SM-EW90 5 port junction box. I use the bike for long time trials, 12/24 hr. and want to change to regular aero bars. I have a pair of ST-6871 11s shifters I will use on the base bar and will use the same aero bars and bar end shifters. I want to know if the TT shifters will be compatible with the junction box I have or I need another one. Shifters cam with cables and the end plugs look like the same.

I am also building a Dogma F10 as a “climbing bike”. My intention is to use the 6870 brake/shifters on that bike (along with the horn bars off of the S5. I want a new Di2 system for the F10 that will be compatible with the “old” shifters. Will probably also install aero bars and bar end shifters Both new) as well (similar to what I have currently on the S5.) DO I go with a 2nd gen. system or the newer e-Tube system.

I have an Ultegra 6870 Di2 set up all working fine and I’ve been trying to pair my Garmin Edge 1000 with the system. I have an SM-EWW01 connected at the RD but have so far failed to get the Garmin & Di2 to talk to each other. All my tech stuff is Apple. I tried going through the E-Tube application on my iPad which also failed. All I can think of is either; the EWW01 is not working as it should or maybe I have the wrong battery? (Not sure what the latter is but my charger is a BCR2 so am assuming the battery is a BTR2)

I think your problem is that your components need firmware upgrade and the system needs to “recognise” the ant+ unit. I take it you have the SM-EW67-A-E Ultegra 3-Cable Junction with the external battery?. You will either need to “borrow” a PCE unit to update your system or if one of your mates has a Di2 system with an internal battery you can change out the SM-EW67-A-E Unit with their SM-EW90-A junction and update your system via their battery charger and a laptop with the ETube software

Ok sorry I assumed wrong. The part number of what you said above is for the old style Ant+ only model ( I also have two of them on my Di2 bikes and they work fine, one has internal battery and the other external). I assume that you have already doine this but I will say it anyway….With what you have just said do you have the internal battery charger with the usb that you connect to a PC/laptop? if so have you downloaded the etube software? if so then plug your cable into the A port and let the software recognise your system and do its connection check. On the screen the items will show up on the graphic. then go back to the main screen and you will see a button for firmware update, press that and the system will update the firmware to the latest.

The part number you mention ( SM-EWW01 ) will NOT communicate with your Ipad as it is not bluetooth

Once done get your garmin to look for the ant+ unit for which you may need to set bike up on a stand and change gears a bit till it “kicks” system into action. All being well it should then show the gear page and you will be a happy bunny.
As I hinted before, I have the Ultegra 6870 set up on my bike and that is the one with external battery

Thanks again – becoming clearer – yes I have a charger (SM BCR2) and the USB port/cable but my laptop is an Apple (without Windows) so I’ve not managed to download the E-tube software and make that apparently critical step (hence my attempts through the E-Tube App on my iPad). I guess I’m going to have to find a friendly lbs with a PC who can do the firmware upgrades for me. Still not sure whether I need a different battery?

Try your garmin and see if it picks up the Ant+ part without plugging it in to a PC or take it to LBS, remember you may need to change gears for it to register on your garmin. As far as battery goes , its only the high spec battery that allows the Bluetooth connection thingy to work to allow full access to the etube software on the ipad. The part number you gave is the Ant+ only

Hi Malcolm – finally sorted. Not sure what happened – partial download or corrupted pairing? In the end I tried a basic fix and simply unplugged the d-fly unit from the battery, deleted the sensor from the Garmin, connected everything back together, tried a new pairing and hey bingo, it all now works. Next thing will be a battery & d-fly unit upgrade with Bluetooth so I can mess about on my iPad and shuffle stuff around. Thanks for your help

Great stuff, hope you enjoy. I also am waiting on the battery upgrade (looking on ebay and the likes for a good deal…) I quite fancy the smart gear changing but the basic ant+ data good for now. Glad to help

Carlton thanks for this extremely informative site. So far it has answered all of my questions. So much so, I am about to order the new 2018 Ultegra Di2 upgrade kit. I’ll need to use a 5 port junction port so I can later add the E-Tube bar-end plug. My only worry is getting the cable from the RD thro the chainstay and past the BB. I currently have an internal RD mech cable but it is very thin. I might have a dummy run with some electrical cable to see if it goes thro.

Could I pick your brains please?
I finally connected the Ew-wu101 today. I have the correct BT internal battery. There were 5 updates needed through the app on my iPhone. I did the 1st 4, but the app crashed @ 48% on the 5th update – the internal battery. Now the whole system is dead. The battery won’t charge. I have the SM-PCE1 box. It won’t recognise the system as it is. If I disconnect the internal battery it recognises everything else (but says the system needs a battery to operate). If I connect the battery directly it is not recognised. Any ideas? It looks like I have to get the battery updated to move forward, but I can’t get anything to recognise it.

I have the required hardware for synchro shift and all firmware is up to date. I’ve been using it (and loving it) for several months now. I recently had to disconnect the battery as I removed the seat post. Whilst I was at it I disconnected and reconnected a couple wires for a better cable run. Now its all back together and I can’t get synchro shift to work.

The button on junction box A still works (to set into bluetooth mode or adjust mech trim), but double clicking does not change between shifting modes. Its basically stuck in mode 1 (traditional shifting) which is working fine on both derailleurs, but I can’t get it to change into modes 2 or 3.

I’d be very grateful if you could come up with a suggestion as to what I have done and how it can be fixed.

About ready to make the jump to electronic shifting, have an F10 frame here which has the removable cap, which -as I understand it- is replaced by a combination charge connector and junction box all-in-one, referred to as an ‘E-link’ port(?).
The bike has been a build project for my son to learn about how things go together, get adjusted, why torque wrenches are important and how to use/store one, etc.
I’m trying to plan out everything I’ll need, but I’m a little confused about which battery, how it mounts in the downtube, and whether I still need an A-junction, etc.
Hunted online for an everything you need to know’ to answer my question, and this seems to be a great resource.
The shifters, FD and RD seem straightforward, and I’ll need cables to connect to those, but it all seems a little vague and mysterious inside the frame.
Thanks in advance for any illumination!

Thanks Carlton. I was told that you needed both sides to work. As a matter of curiosity are the brains in the derailleurs ie the levers/shifters send the signals to the derailleurs and the junctions are just connection facilities?

Carlton, probably can file under ” another stupid question”…I bought the SW-R9150 shifter set. Each sifter comes in a separate bag, one pink, one clear with corresponding different part numbers. Is there any difference, like a left and right, or does it matter. Can’t believe the instruction sheet is so sparse!

Carlton, now that I can figure out my left and right satellite buttons, I’m looking for input as to locating them. 😉
Basically you have a choice of using your index finger or thumb actuation, but if you try to locate for both finger/thumb then neither works very well. Have you used or installed the R9150 shifters? I know a lot of this is personal preference, but if do you have any insight I’d love to here it!

Hey Carlton – thanks for a great page! I’ve just bought a bike equipped with 6770 Di2. I haven’t taken delivery yet but I’m already wondering about tinkering with the system. The chart you and Shimano provide says that the SM-BTR2 battery and the SC-M9050 junction box, which both support synchro shift, are compatible with the rest of the 6770 kit, so is it unreasonable to hope that the 6770 could be persuaded to play along? Is the incompatibility you mention built into the firmware, so that the battery recognises the 6770 RD, for example? Would swapping the RD for a more recent compatible one do the trick?

Hi Carlton, have a Dura Ace 7970 di2 10 speed Giant. The rd-7970 has died and they are now obsolete! Is my only and cheapest alternative to buy an Ultegra 6870 Di2 11 speed gear set? Thanks for your informative site

Geoff, the cheapest option is to buy a used rd-7970 on eBay or similar. They are show up once or twice a month. 6870 Di2 has a much better future ahead for support, but you will need to upgrade everything on your bike, including the rear sprockets and maybe even your wheel. I recommend the eBay option and being patient to find the right part.

Hi, I´m from Spain, sorry for my level of English. I am a triathlete and I have the new Dura Ace 9150 Di2 in my new Scott Plasma Premium aero TT bike. I´m trying to resolve a big problem for me, when I pedaling in aero position over on the extensions I only can change the gears up with one shifter up and the other down (SW-R9160 Time Trial bar-end shifters (pair) also with ST-9071 Dura-Ace Time Trial/Triathlon Dual Control Brake Levers/Shifters).

Synchronized Shifting is a big product, but for us (triathletes) I think that it does not work very well. I need to drop (leave, release) the handlebar of the bike to change gear if I pedaling over the brakes or over the extensions because the all the shifters are configurated with only one button and command.

My doubt, is it possible to configurate the shifters to avoid to drop (leave, release) the handlebar or the extensions? i.e., if I control the bike over the brakes and I want to up one gear I need to drop the handlebar to push the upshift. I know that the symchronized Shifting control this situations but for triathlon we need more availability options.

Thank you so much for your answer. I do not yet understand the reduction of buttons from Shimano. Finally I opted to use the Full Synchro option and left side (handle bar and bar-end buttons) up gear (sprockets) and the right side down, the rest to work efficient is done for the Full Synchro option (up/down chainwheels). The problem here is if you need to up/down quickly the chainwheels you only have the buttons to do it, you can not up/down these one.

I saw a neat setup on GCN a few months back where someone with an aero road bike with etap bought an aero tt handlebar and switched between road and tt handlebars only needing to re-pair the shifters (and also change brake cables).

I’d like to duplicate this setup with ultegra di2 to save cost, but this would mean changing cables. Seems like this is doable as long as I have the handy cable tool, but I still worry regularly changing cables will wear them down, or wear down the junction box. Would that be an issue?

Hi I’m looking at a new bike and tossing up between Dura ace di2 and Ultegra I have had bike shops say Dura ace shifts better but what I can gather the main difference is weight and price just wondering your thoughts. Thanks

I agree with you; the only significant difference are weight and price. Unless you are an ultra competitor or have unlimited money to spend, it’s very difficult for me to recommend Dura-ace. Ultegra offers identical performance at a significantly lower price.

But Dura Ace does have the buttons under the hoods that allow one to scroll thru screens on their bike computer without taking the hands of the bars. Thats a safety feature for me. Does the latest Ultegra have this?

True that! For safety the scroll feature should be added to Ultegra. Adding the DA shifter cost to an Ultegra group is still onerous. Etronics aside, ultegra cassettes are more durable and of course cheaper.

I believe the shifters in the latest version of electronic Ultegra – R8050 – do have the same remote switches on top of the hoods as Dura-Ace. However for the next part I’m not really sure, but knowing Shimano, you may need the updated transmitter, WU101 or WU111, and maybe even the most recent battery BT DN110 to fully utilise the remote switches?

Hello, Carlton. You know how to solve a lot of problems with di2. I think that you can help me to fix problem with di2 rd-9070. Rear derailleur does not shift to 10th and 11th gear. Firmware updated successfully. I tried to fix problem using crash mode. In this mode RD doesn’t shifts to this to gears too… when I connect my di2 to PC RD sets to 9th gear but on PC indicates 11th gear. Carlton could you help to solve this problem? RD wasn’t damaged never. One day it’s stop working correctly.

Hello, Carlton. Today I learned shimano manual. Setup procedure did not help. I tried to setup using pc and Etube programm. Programm shows me that I should make a request to Shimano. May be it is mechanical problems?

Good Day Carlton, i run 3 bikes with the 9070 groupset. i am a mobile bike mechanic. i have all the latest software and components. when i activate “Synchro-Shift” on either bikes, i get a tremendous battery drain overnight. it was down to 15% yesterday after a full charge the previous day, if i disable the s/shift, there is no battery drain. can u please give me a soiution? my limit screws are all adjusted perfectly. thanks